The invention relates to sealing facilities in general, and more particularly to improvements in seats which can be used with advantage in motor vehicles. Still more particularly, the invention relates to improvements in seats with adjustable back rests which are connected with or adjacent to arm rests.
German Pat. No. 26 48 951 to Goldner et al. discloses a seat which is intended for use in motor vehicles and wherein the rear portion of the frame which forms part of the body supporting unit of the seat carries two plates flanking the frame and each pivotably supporting the respective frame member of the back rest. The means for pivotably mounting the back rest on the body supporting unit includes two hinges having a common axis and each connecting one of the plates to the adjacent frame member of the back rest. Each frame member of the back rest carries an arm rest which is pivotably secured to the respective frame member at a level above the common axis of the hinges. A link connects each arm rest to the body supporting unit of the seat. The purpose of the links is to prevent excessive changes of orientation of the arm rests in response to adjustments of inclination of the back rest relative to the body supporting unit of the seat. A cylinder and piston assembly is provided to change the inclination of the back rest.
A drawback of the patented seat is that the position of the back rest (and hence the position of each arm rest) is not sufficiently stable. For example, the inclination of the back rest can change in response to leakage of pressurized fluid from the cylinder and piston assembly, and this can result in a movement of the arm rests to positions which are not comfortable to the occupant of the seat. Therefore, many recent types of seats for motor vehicles are equipped with gear transmissions which are associated with or embodied into the hinges and ensure reliable retention of the back rest in a desired position of inclination with reference to the body supporting unit.
Another drawback of the patented seat is that the inclination of the back rest relative to the body supporting unit can be changed only within a relatively small angle. This is attributable to the fact that the frame members of the back rest extend downwardly beyond the respective hinges and their lower end portions are connected to the cylinder and piston assembly.